The present invention relates to a one-piece mold for forming a bathing unit that comprises as a single piece a bathtub and bathtub surround or a single-piece shower and shower surround, with such mold forming encroachments within the bathing unit that incorporate negative draft angles. The present invention further relates to a method of molding such a bathing unit.
Molded bathing units that comprise as a single piece a bathtub and bathtub surround or shower and shower surround are preferable to bathing units molded or formed from two or more separate pieces. Bathing units molded as a single piece are typically more economical to produce and often have superior structural and design characteristics for certain applications. Specifically, such bathing units are ideal for use in space-limited areas, such as the bathroom of a recreational vehicle.
Typically, one-piece molds for bathing units are configured so that encroachments molded into the bathing unit incorporate positive draft angles. It has long been believed in the art that avoiding negative draft angles in the mold and item to be molded is necessary to permit the molded item to be removed from the mold without breaking the molded item or the mold. Using molds and methods of molding known in the art, forming an encroachment with a negative draft angle in a molded item would require either the use of a two-piece mold, or the breaking or cutting of the molded item to enable removal of the item from the mold.
The inability of one-piece molds and methods of molding known to the art to accommodate encroachments with negative draft angles significantly limits the design features possible for bathing units formed by such molds and methods of molding. To avoid negative draft angles, molds and methods of molding known to the art form each encroachment in a bathing unit as a “pillar” running at a positive draft angle from the floor of the bathing unit to the height desired for the feature. Seats, benches, shelves, soap dishes, sump walls, and other encroachments within a bathing unit are typically funned by the upper face of such “pillars,” as shown in FIG. 2. This configuration permits removal of the bathing unit from the mold. However, the necessity of forming a pillar extending to the floor of the bathing unit to accompany each desired encroachment reduces the space available to the user within the unit, and specifically reduces floorspace available to the user.
As a result, molds and methods of molding known to the art typically limit the number and size of encroachments—and thus, the number and size of features such as seats, shelves, benches, and dishes within such bathing units—to preserve space and floorspace within the unit. Further, molds and methods of molding known to the art cannot easily incorporate encroachments directly above or directly below other encroachments because of the difficulty of forming a positive draft angle for all but the lowermost encroachment. This significantly limits the design possibilities of bathing units formed by molds and methods of molding known to the art.
Accordingly, it is desirable to provide a one-piece mold and method of molding using a one-piece mold that is capable of producing an item, with encroachments that incorporate negative draft angles, that can be removed from the mold in a single piece without breaking the mold or the item. Preferably, such item is a bathing unit.